The invention relates to an air heater comprising a number of parallel strip-shaped sheet metal heat sinks mounted in a frame, a number of PTC tablets, a large number of heat-conducting lamellae extending transversely to the heat sinks and electrical connection means.
A similar air heater is known from EP-A-0,350,528 (David & Baader).
The device can be used on automobiles to heat ventilation air supplied to the windshield, before the motor is warm enough to take over the air heating through the normal heating radiator. One advantage is that cold air can be heated electrically without any advanced regulator mechanism, and the temperature cannot rise above a level dictated by the properties of the PTC material.
In the known device the heat sinks consist of separate metal strips and the lamellae are always attached to the heat sinks by soldering. The PTC tablets lie flat against the heat sinks without being glued to them. This presents a risk of corrosion at the contact surfaces between PTC tablets and heat sinks, leading to a bad electrical contact. Two of the four frame sides or borders consist of two mutually displaceble lengths, between which an undulating spring belt is placed, which presses the inner length onto an adjacent metal heat sink strip and thus clamps the entire package of separate heat sinks, lamellae and loose PTC tablets inside the frame. In addition, the PTC tablets are kept in place by an extra plastic holder. The production, separately, of heat sink strips and lamellae, the soldering of the films and the assembly into a unit, leads to an expensive construction. Then, in order to have a good contact between the PTC tablets and the heat sinks, they have to be precisely placed flat on one another; the tolerances are small, and this also increases the cost.